A bee inspector checks on a frame of bees to assess the colony strength near Turlock, Calif., in February. More than 30 percent of America’s bee colonies died off over the winter. Photo: Gosia Wozniacka/AP

According to a new survey of America’s beekeepers, almost a third of the country’s honeybee colonies did not make it through the winter.

That’s been the case, in fact, almost every year since the U.S. Department of Agriculture began this annual survey, six years ago.

Over the past six years, on average, 30 percent of all the honeybee colonies in the U.S. died off over the winter. The worst year was five years ago. Last year was the best: Just 22 percent of the colonies died.

“Last year gave us some hope,” says Jeffrey Pettis, research leader of the Agriculture Department’s Bee Research Laboratory in Beltsville, Md.

But this year, the death rate was up again: 31 percent.

Six years ago, beekeepers were talking a lot about “colony collapse disorder” — colonies that seemed pretty healthy, but suddenly collapsed. The bees appeared to have flown away, abandoning their hives.

Beekeepers aren’t seeing that so much anymore, Pettis says. They’re mostly seeing colonies that just dwindle. As the crowd of bees gets smaller, it gets weaker.

“They can’t generate heat very well in the spring to rear brood. They can’t generate heat to fly,” he says.

Farmers who grow crops like almonds, blueberries and apples rely on commercial beekeepers to make sure their crops get pollinated.

But the number of honeybees has now dwindled to the point where there may not be enough to pollinate those crops.

Pettis says that this year, farmers came closer than ever to a true pollination crisis. The only thing that saved part of the almond crop in California was some lovely weather at pollination time.

“We got incredibly good flight weather,” Pettis says. “So even those small colonies that can’t fly very well in cool weather, they were able to fly because of good weather.”

A bee collects nectar from a fruit tree in West Bath, Maine. The number of honeybees has now dwindled to the point where there may not be enough to pollinate some major U.S. crops. Photo: Pat Wellenbach/AP

Pettis says beekeepers can afford to lose only about 15 percent of their colonies each year. More than that, and the business won’t be viable for long. Some commercial beekeepers are still in business, he says, just because they love it.

“It’s just something that gets in your blood, so you don’t want to give up. [You say,] ‘OK, it’s 30 percent this year; I’ll do better next year.’ We’re very much optimists,” he says.

Beekeepers have a whole list of reasons for why so many colonies are dying. There’s a nasty parasite called the Varroa Mite, which they can’t get rid of. There are also bee-killing pesticides. And there are just fewer places in the country where a bee can find plenty of flowering plants that provide nectar and pollen.

That was especially true this past year. The same drought that left Midwestern corn fields parched and wilting also dried up wildflowers and starved the bees.

That was a natural disaster. But May Berenbaum, who chairs the Department of Entomology at the University of Illinois at Urbana-Champaign, says that most of the changes in the landscape are the result of people’s decisions about what to do with their land.

“I just wish there were more incentives for people — not just farmers — to plant a more diversified landscape that provides nutritional resources for all kinds of pollinators,” she says. “Plant more flowers! And be a little more tolerant of the weeds in the garden.”

More controversial is the role of pesticides. Some beekeepers and environmentalists are calling for tighter restrictions on the use of one particular class of pesticides called neonicotinoids. Europe is about to ban some uses of these pesticides. But U.S. farmers and pesticide companies are opposed to any such move here, and the Environmental Protection Agency says it’s not yet convinced that this would help bees very much.